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Central Processing Unit (CPU)
MC9S12DP256 — Revision 1.1
Central Processing Unit (CPU)
Programming Model
STAR12 CPU registers are an integral part of the CPU and are not
addressed as if they were memory locations.
Figure 1 Programming Model
Accumulators
A and B are general-purpose 8-bit accumulators used to
hold operands and results of arithmetic calculations or data
manipulations. Some instructions treat the combination of these two
8-bit accumulators as a 16-bit double accumulator (accumulator D).
7
15
15
15
15
15
D
IX
IY
SP
PC
AB
0
0
0
0
0
0
70 8-BIT ACCUMULATORS A & B
16-BIT DOUBLE ACCUMULATOR D
INDEX REGISTER X
INDEX REGISTER Y
STACK POINTER
PROGRAM COUNTER
OR
NSXH I ZVC CONDITION CODE REGISTER
STOP DISABLE (IGNORE STOP OPCODES)
CARRY
OVERFLOW
ZERO
NEGATIVE
IRQ INTERRUPT MASK (DISABLE)
HALF-CARRY FOR BCD ARITHMETIC
XIRQ INTERRUPT MASK (DISABLE)
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